use an APL to estimate unavoidable downtime for Cata Arms

Arms is a downtime spec in Cata: you do not have enough cooldowns
or Rage to fill every GCD, so some are unavoidably empty.

this uses an APL-based approach to attempt to identify situations
where there isn't an appropriate spell to cast. such periods are then
added to the `AlwaysBeCasting` as "uptime" regions, boosting overall uptime

src/analysis/classic/warrior/arms/modules/features/AlwaysBeCasting.ts

@@ -1,7 +1,29 @@
+import CLASSIC_SPELLS from 'common/SPELLS/classic';
 import { ThresholdStyle, type NumberThreshold } from 'parser/core/ParseResults';
+import { AplChecker, build } from 'parser/shared/metrics/apl';
 import CoreAlwaysBeCasting from 'parser/shared/modules/AlwaysBeCasting';
+import SpellUsable from 'parser/shared/modules/SpellUsable';
+import * as cnd from 'parser/shared/metrics/apl/conditions';
+import RESOURCE_TYPES from 'game/RESOURCE_TYPES';
+import { Options } from 'parser/core/Analyzer';
+import Events, { AnyEvent, FightEndEvent } from 'parser/core/Events';
+
+export default class AlwaysBeCasting extends CoreAlwaysBeCasting.withDependencies({
+  spellUsable: SpellUsable,
+}) {
+  private aplChecker;
+
+  private lastUptimeStart?: number;
+
+  constructor(options: Options) {
+    super(options);
+
+    this.aplChecker = new AplChecker(apl, this.owner.info);
+
+    this.addEventListener(Events.any, this.processAplDowntime);
+    this.addEventListener(Events.fightend, this.finalize);
+  }
 
-export default class AlwaysBeCasting extends CoreAlwaysBeCasting {
   get downtimeSuggestionThresholds(): NumberThreshold {
     return {
       actual: this.downtimePercentage,
@@ -13,4 +35,60 @@ export default class AlwaysBeCasting extends CoreAlwaysBeCasting {
       style: ThresholdStyle.PERCENTAGE,
     };
   }
+
+  private processAplDowntime(event: AnyEvent) {
+    // the idea here is that we add "uptime" from the point where the APL says "don't cast anything" to the next point where the APL says "cast something"
+    const expectedCast = this.aplChecker.expectedCast();
+
+    this.aplChecker.processEvent(event);
+
+    if (expectedCast && this.lastUptimeStart && event.timestamp >= this.owner.fight.start_time) {
+      // apl: "cast something"
+      if (this.lastUptimeStart !== event.timestamp) {
+        this.addNewUptime(this.lastUptimeStart, event.timestamp, false, 'Arms APL-based downtime');
+      }
+      this.lastUptimeStart = undefined;
+    } else if (!expectedCast && !this.lastUptimeStart) {
+      // apl: "don't cast anything"
+      this.lastUptimeStart = event.timestamp;
+    }
+  }
+
+  private finalize(event: FightEndEvent) {
+    if (this.lastUptimeStart) {
+      this.addNewUptime(
+        this.lastUptimeStart,
+        event.timestamp,
+        false,
+        'Arms APL-based downtime (finalizer)',
+      );
+    }
+  }
 }
+
+const apl = build([
+  {
+    spell: CLASSIC_SPELLS.REND,
+    condition: cnd.debuffMissing(CLASSIC_SPELLS.REND_DEBUFF),
+  },
+  {
+    spell: CLASSIC_SPELLS.COLOSSUS_SMASH,
+    condition: cnd.debuffMissing(CLASSIC_SPELLS.COLOSSUS_SMASH),
+  },
+  CLASSIC_SPELLS.MORTAL_STRIKE,
+  {
+    spell: CLASSIC_SPELLS.EXECUTE,
+    condition: cnd.inExecute(),
+  },
+  {
+    spell: CLASSIC_SPELLS.OVERPOWER,
+    condition: cnd.buffPresent(CLASSIC_SPELLS.TASTE_FOR_BLOOD),
+  },
+  {
+    spell: CLASSIC_SPELLS.HEROIC_STRIKE,
+    condition: cnd.or(
+      cnd.buffPresent(CLASSIC_SPELLS.BATTLE_TRANCE),
+      cnd.hasResource(RESOURCE_TYPES.RAGE, { atLeast: 800 }, 0),
+    ),
+  },
+]);

src/common/SPELLS/classic/warrior.ts

@@ -115,6 +115,11 @@ const spells = {
     name: 'Taste for Blood',
     icon: 'ability_rogue_hungerforblood.jpg.jpg',
   },
+  BATTLE_TRANCE: {
+    id: 12964,
+    name: 'Battle Trance',
+    icon: 'inv_helmet_06',
+  },
   PUMMEL: {
     id: 6552,
     name: 'Pummel',
@@ -130,6 +135,11 @@ const spells = {
     name: 'Rend',
     icon: 'ability_gouge.jpg',
   },
+  REND_DEBUFF: {
+    id: 94009,
+    name: 'Rend',
+    icon: 'ability_gouge.jpg',
+  },
   RETALIATION: {
     id: 20230,
     name: 'Retaliation',

src/parser/shared/modules/AlwaysBeCasting.tsx

@@ -100,7 +100,7 @@ class AlwaysBeCasting extends Analyzer {
   }
 
   /** Validates and logs inputs, then adds to activeTimeEdges list */
-  private addNewUptime(start: number, end: number, isHealingAbility: boolean, reason: string) {
+  protected addNewUptime(start: number, end: number, isHealingAbility: boolean, reason: string) {
     DEBUG &&
       console.log(
         `Active Time: adding from ${reason}: ${this.owner.formatTimestamp(start, 3)} to ${this.owner.formatTimestamp(end, 3)}${isHealingAbility ? ' (heal)' : ''}`,